Automatically regulating the intensity of a printing light



p 1935- J. R. BALSLEY 1,999,556

AUTOMATICALLY REGULATING THE INTENSITY OF A PRINTING LIGHT Filed Dec. 5,1928

l'V/T ss Patented Apr. 30, 1935' PATENT OFFICE AUTOMATICALLY REGULATING THE IN- TENSITY OF A PRINTING LIGHT James R. Balsley', New York, N. Y., asslgnor, by mesne assignments, to Movietonews, Inc., New York, N. Y., a corporation of New York Application December 5, 1928, Serial No. 324,016

'2 Claims.

This invention relates to certain new and useful apparatus for automatically regulating the intensity of a printing light.

The main object of the invention is the production of a regulating, apparatus in combination with an apparatus for printing a sound positive from a sound negative by means of which the intensity of the printing light is automatically regulated to the correct value in accordance with the average density of the portion of the sound negative which is about to be subjected to the printing light whereby a more efiective positive is produced.

Other objects and advantages relate to the details of the apparatus and the association and relation of the parts thereof all as will more fully appear from the following description taken in connection with the accompanying drawin in which:-

The figure is a diagrammatic illustration of an embodiment of the invention.

As illustrated in the drawing the negative sound record film I and the film 2 which is adapted to constitute the positive sound record are moved in overlying relation in any suitable and well known manner between gate members 3 and 4 which may be of any usual and well known construction. The gate member 3 is provided in the usual manner with an opening or slot 5 of suitable size for efiecting printing. a The printing light may be an ordinary incandescent lamp 6, the light from which passes through the slit 5. If desired the light from lamp 6 may be diffused in any suitable and well known manner.

The lamp 6 is maintained lighted by line current flowing in a circuit connected to the lamp, such circuit including a rheostat 1. The structure so far described may however be of any suitable and well known construction adapted for printing a positive from a negative, the invention here residing in the combination with such apparatus of automatic means for regulating the intensity of the light rays emanating from the printing light 8. For the purpose of regulating such intensity of such light in accordance with the average density of the sound record which is about to be subjected to such light there is illustrated a photoelectric cell 8 of any suitable and well known construction which is subjected to rays of light produced, as for instance, by a lamp 9 and passed through a slit l0 and through the sound record upon the negative I and thereupon as modified by the sound record falls upon the photoelectric cell 8.

The slit or opening Ill should be of such a size so that the total light falling upon the photoelectric cell passes at any instant through a section of the negative sound record several wave lengths long of the lowest note recorded. One

full wave length should accomplish the desired result but several will reduce error that might result because of the non-uniformity of the film itself.

The total, light available for modulating the photoelectric cell to regulate the intensity of light 6 is then proportional to the average density of the negative or what would be obtained from an unmodulated section of the sound track of the film.

The lead II from one electrode of the photoelectric cell is tapped into the grid filament circuit of an audion I! which includes grid l3, filament l4 and plate I5. The .lead Hi from the other electrode of the photoelectric cell 8 is tapped into the plate filament circuit of the audion l2, such circuit including an iron core magnet l1 and a variable resistance l8 which resistance may also bridge-the terminals of the filament M. The supply line for current to the audion circuits may be connected to the opposite ends of the resistance l8 with a voltage regulator l9 across the circuit. The iron core magnet l1 and the rheostat I in which the contact arm 20 is normally drawn by spring 2| in a direction opposed to the magnetic pull of magnet l'l constitutes a relay of the type in which variation in current flowing through the magnet ll moves the contact arm 28 against the action of spring 2| to vary the resistance included in the printing light circuit.

It will be apparent, therefore, that variations in the current flow in the audion circuits as efiected by variations in the intensity of the light to which photoelectric cell 8 is subjected will include a variation of the current fiowing in the coil of magnet l1 thereby varying the magnetic pull of the iron core magnet I! to effect movement of the contact arm 20 to vary the resistance in the circuit of the printing light 6 in accordance with the average density of that portion of the record and relation 0! the parts thereof without departing from the spirit or this invention as set forth in the appended claims.

I claim:

1. A printing apparatus including a printing light, means for simultaneously moving a negative sound record and a film adapted to constitute a positive sound record in overlying relation, a printing light to which the said negative is exposed, and means for varying the intensity of the printing light in accordance with the average density of a portion of the sound record that has not yet reached the point of exposure of the printing light, said means comprising an electric circuit, including a photo-electric cell connected in circuit with an audion amplifier, means for subjecting the photo-electric cell to light waves varied in accordance with the average density of said portion of the sound record, a circuit connected to the printing light and including a resistance, electro-magnetic means including a coil connected in the output circuit of said audion amplifier for varying the resistance in said light circuit in accordance with variations in the photo-electric cell circuit and means for controlling the steady component of current through said coil.

2. A printing apparatus including a printing light, means for simultaneously moving a negative sound record and a film adapted to constitute a positive sound record in overlying relation, a printing light to which the said negative is exposed, and means for varying the intensity of the printing light in accordance with the average density of a portion of the sound record that has not yet reached the point of exposure of the printing light, said means comprising an electric circuit, including a photo-electric cell connected in circuit with an audion amplifier, means for subjecting the photo-electric cell to light waves va ried in accordance with the average density of said portion of the sound record, a circuit connected to the printing light and including a resistance, an electro-magnet connected in the output circuit of said audion amplifier and disposed to efiect a variation of the resistance included in the printing light circuit a manually adjustable source of direct current potential for said audion output circuit and for adjusting the steady current component through said electro-magnet, and means for maintaining the voltage of said source at a constant value.

JAMES R. BAISLEY. 

